(1) Field of the Invention
This invention relates to key operated percussion devices such as pianos and, more specifically, to the hammer assemblies of such devices. A hammer assembly according to this invention comprises: a hammer 40; a hammer shank 30; a tubular lever interface 20; and a moveable knuckle 240.
(2) Description of Prior Art
A piano produces sound as a result of a complicated mechanical chain reaction which starts with the pianist depressing a piano key which in turn actuates a piano action 15 associated with a key 10 which in turn rotates a hammer assembly associated with the piano action which in turn strikes a piano string or strings 35 to make sound.
More specifically, a depressed key 10 gives rise to motion of the damper head assembly (not shown), separating the damper head from the associated set of strings 35, setting the strings ready to accept vibrations. The piano strings 35 are located just above the hammer. The depressed key 10 also actuates the piano action 15 thereby pushing or “throwing” the associated hammer 40 and hammer shank 30 into the associated set of strings or string 35. The hammer 40 strikes the strings, generating a piano tone. The piano action 15 then receives or “catches” the hammer 40 and hammer shank 30 after it strikes the strings 35 and rebounds back against the action 15. When the pianist releases the depressed key 10, the key 10 returns to the rest position, and permits the damper head assembly to return contact with the vibrating strings 35. The vibrations are absorbed by the damper head assembly, and the piano tone is terminated.
With a grand piano 45, a certain amount of kinetic energy is required when depressing a key 10 in order to move a hammer 40 as imparted by the piano action 15 to the hammer shank (20 and 30). When a key 10 is depressed, the repetition base 70 is pushed up pivotally about the repetition flange 90. The jack 50 is simultaneously moved upward pivotally about point 100 in the clockwise direction and pivotally about repetition flange 90 in the counterclockwise direction, resulting in a general upward motion. The jack 50 lifts the knuckle 80, which also moves upward from double pivot motion, this time about the repetition flange 90 and point 110. The jack 50 raises the knuckle 80 along with the hammer shank (20 and 30) thereby lifting the hammer 40 upwards towards the piano strings 35. The knuckle 80 also slides along the guide surface of the balancier 60. These both cause the hammer 40 to move upward by rotation about point 105 towards the set of horizontally stretched strings or string 35 associated with that key 10. The hammer 40 moves with “free rotation” powered by the knuckle 80 driven by the jack 50. The hammer shank 30 is further rotated and disconnects from the balancier 60 in order for the hammer 40 to strike the strings 35. There is one hammer assembly and one piano action for each of the eighty-eight keys of a grand piano.
At this point, on both grand pianos and upright pianos, conventional wood hammer shanks 30 bend somewhat before whipping around to strike the strings 35. This phenomenon can be verified by simple high speed photography of hammer motion resulting from practically every instance of piano playing. The more virtuosic the particular piano piece played, the greater the bending or deflection of the hammer shanks 30. This is because virtuosic piano pieces require greater key depression strength with faster key depression repetitions, which results in more forceful and more frequent hammer assembly rotations. As with all deflection motion, the greater the force applied on the body, the greater the deflection.
Since the energy absorbed by a bending of hammer shank 30 does not directly translate into the production of music, it is wasted energy or energy loss of the system. Thus, more key depression energy is required in order to produce music as a result of the bending of a hammer shank 30. Therefore, the elimination of hammer shank 30 deflection lowers the threshold energy key depression requirement for the creation of sound. Hence the elimination of hammer shank 30 deflection results in a more responsive piano that requires less effort to play.
Additionally, the weight of the hammer assembly affects the responsiveness of the piano action. The leverage of most grand piano actions is about 5-7 to one at the hammer assembly. Thus, a slight increase in the hammer assembly weight or shank weight is quickly reflected in the key down weight. I.e., an increase in weight of shank 30 results in an exponential increase in the energy requirement for key depression. Likewise, a decrease in shank weight results in an exponential decrease in key depression energy. Thus, a lighter hammer assembly results in a more responsive piano that requires less effort to play.
The grand piano hammer assembly of prior art comprises a one-piece hammer shank 30 that has a cylindrical end and a forked end 88. The Forked end 88 attaches directly to a shank flange 95 by a hinge pin 93. The shank flange 95 is attached to the shank rail on the piano (not depicted). Hammer shank forked end 88 needs to be wider than the shank portion because it is at this location where the knuckle 80 is attached to the member 30. Prior art knuckles consist of a spline 82, resilient inner core cushion 84, and synthetic buckskin wear surface 86. The forked end 88 of the shank 30 further comprises a slot 89 into which the knuckle spline 82 is secured, thereby connecting the knuckle 80 to the hammer shank 30 to form a sub-assembly. The forked end 88 needs to be wide at this location because the slot 89 weakens this end. Because the slot weakens the hammer shank, more deflection and bending of the shank occurs than would happen if the slot 89 were not present. As stated above, the hammer assembly must withstand deflection forces caused by the acceleration of the hammer 40 towards the string(s) 35. The more deflection, the less efficient the hammer assembly is at accelerating the hammer 40 towards the string(s) 35. Also, as a result of being wider, the forked end 88 is heavier, which also greatly reduces efficiency of this motion.
The hammer 40 is attached to the sub-assembly at the cylindrical end or other end of the hammer shank 30. The cylindrical end of the shank 30 is inserted into a hole on the hammer 40. Both knuckle and hammer attachments are typically achieved by gluing means. The shank 30 is made of wood throughout, typically hornbeam or maple wood. The prior art does not consist of separate tubular lever interface 20 and hammer shank 30 components.
Prior art hammer shanks 30 come in one standard diameter or cross sectional area that can be thinned to reduce mass. The reduced mass is particularly required in the treble section because of the need to make the hammer rebound more quickly from the string. Prior art hammer shanks 30 are thinned, in two or three increments, as the pitch of the string or strings 35 associated with the particular hammer shank increases. For manufacturing efficiency, this thinning is not continuous but rather is stepped by three separate groups—“thin”, “medium”, and “thick”. “Thick” hammer shanks 30 are not trimmed at all and are used on the bass end of the piano. The deflection referenced above occurs in the hammer shank (20 and 30).
Relative to more modern materials, such as composites or plastics, wood is an inefficient raw material from which to manufacture piano action components. Wood action pieces must be drilled to produce the holes required for pivotal connections and assembly with other action components. The hole-drilling process is a laborious and costly process as compared to the production of molded piano action pieces with holes accurately formed therein during the initial molding process. Also, the production of any finished wood piece necessarily involves relatively large quantities of wasted material in the form of saw dust, which is inefficient and wasteful.
Wood is hydroscopic, i.e. wood swells, shrinks, or twists as its moisture content changes in response to the environment. This can cause binding in the action. Additionally, after repeated occurrences, this causes compression of the wood leading to failure of the piano action component thus requiring excessive in field service. For instance, wood flanges often crack due to expansion from a rise in moisture content, as the screw crushes the wood in the flange where it is fastened to the rail.
Moreover, wood has different strengths in different directions, complicating manufacturing processes, also resulting in reduced manufacturing efficiencies. Additionally, wood has inferior rigidity and strength as compared to modern composites and plastics. In particular, rigidity and strength is of the utmost importance to the hammer assembly portion of the complicated mechanical chain reaction of a piano.
Finally, the lifespan of wood piano action components is limited as compared to that of other materials such as composites or plastics because wood over time deteriorates becoming weak and unserviceable. On the other hand, composite piano action components would have several times the life span of that of their wood counterparts and thus result in more efficient manufacture and maintenance of a piano.